We propose to develop a new sweat test kit that will be a diagnostic screening tool for detecting cystic fibrosis (CF) in infants. The test will produce a quantitative chloride value with the same accuracy as the current "gold standard" test known as the Gibson-Cooke Sweat Test (GCST). This new test will be easy-to-use, can be performed in a fraction of the time as the GCST, and require only 3-10 milligrams of sweat to produce an accurate test result. The main goals of Phase I are to produce a test kit that will perform well in clinical studies, develop a simple method to interpret the test results, and construct a calibration tool to insure the stability of the test. A new quantitative sweat test is needed because the prognosis for patients with CF improves markedly with early detection and subsequent prophylactic therapy. General agreement exists on the need to develop a screening test for asymptomatic infants before 6 weeks of age. Current techniques for diagnosis of CF are poorly suited to broad- based screening because of their cost, their high error rate, and or the practical and psychological burden they place upon the parents. This new test will address all these issues. PROPOSED COMMERCIAL APPLICATIONS: This research will lead to the development of a new quantitative chloride sweat test that will make it possible to screen asymptomatic infants for CF. The test will be cost-effective, easy to use, and therefore can be adapted to broad-based screening.